JPH05342374A - One-chip microcomputer - Google Patents

Abstract

PURPOSE:To easily change the program code and data in a ROM. CONSTITUTION:A flash EEPROM 2 where the program code, the data code, etc., are stored is provided, and this EEPROM is divided into a program code storage area 4, a data code storage area 5, and a bootstrap storage area 6, and change data from an external RAM 8 is written in areas 4 and 5 by the program stored in the bootstrap storage area 6. Thus, data is easily changed with a one-chip microcomputer 7 packaged on a substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a program code,
The present invention relates to a one-chip microcomputer having a ROM that stores a data code.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a conventional one-chip microcomputer, in which 1 is a CP.
U, 3 are RAMs, such as working SRAMs, 9 is a one-time RO for storing program codes and data codes.
ROM composed of M, EPROM, etc., 10 is CPU1, R
It is a one-chip microcomputer composed of AM3 and ROM9.

Next, the operation will be described. One time R
In the one-chip microcomputer 10 having a built-in ROM 9 such as OM or EPROM, a one-time ROM having the program code and data code built therein
Alternatively, when writing to the EPROM, writing is performed using an EPROM writer.

[0004]

Since the conventional one-chip microcomputer is constructed as described above,
Since the program code and the data code are written in the built-in one-time ROM or EPROM using the ROM writer, the one-chip microcomputer 10 is mounted when the program code and the data code are frequently changed. It is impossible to rewrite the program code and data code on the board. Therefore, the one-chip microcomputer 10 can be mounted on the board using a socket and can be removed, or the one-chip microcomputer 10 can be removed. External R
There is only a method of changing the program code and the data code by providing the OM and writing the program code and the data code in the ROM, and there is a limitation on the board space, a problem of durability, and the one-chip microcomputer 10 is a flat package. In the case of, there was a problem that it was difficult to mount the socket due to its structural and dimensional problems.

The present invention has been made in order to solve the above problems, and a program code and a data code inside a one-chip microcomputer are mounted on a substrate on which the one-chip microcomputer is mounted. An object of the present invention is to obtain a one-chip microcomputer capable of realizing the erasing function and the writing function without removing the microcomputer.

[0006]

A one-chip microcomputer according to the present invention has an electrically erasable flash EEPROM incorporated therein, and the flash EEPROM is segmented.
It is a program code storage area, a data code storage area, and a bootstrap storage area for reading and writing data from these areas.

[0007]

In the one-chip microcomputer according to the present invention, the built-in flash EEPROM is segmented, and the program code is mounted on the substrate on which the one-chip microcomputer is mounted in a state where the one-chip microcomputer is mounted on the substrate. Alternatively, the data code can be independently rewritten.

[0008]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a CPU, 2 is a segmented flash EEPROM, 3 is a RAM, and 7 is a CPU.
1, one-chip microcomputer with built-in flash EEPROM 2 and RAM 3, 8 flash EEP
This is a RAM used when writing the changed data to the ROM 2.

In the flash EEPROM 2, 4 is a program code storage area, 5 is a data code storage area, and 6 is an initial program for storing a program for reading data from the outside and writing the data in the program code storage area 4 or the data code storage area. A bootstrap storage area for a loader or the like.

Next, the operation will be described. Flash EEPROM 2 inside one-chip microcomputer 7
Is segmented into a program code storage area 4, a data code storage area 5, and a bootstrap storage area 6 such as an initial program loader, and data can be erased and written independently of each other. The bootstrap storage area 6 stores a program for writing data in the program code storage area 4 and the data code storage area 5.

When the data code storage area 5 needs to be changed, the contents of the data code storage area 5 are first erased by an electric erase signal, and the changed data to be written in the data code storage area 5 is written in one chip. The data is written in the RAM 8 externally attached to the microcomputer 7. Next, the program stored in the bootstrap storage area 6 is executed to read the contents of the RAM 8, and the read data is written in the data code storage area 5.

When the program code storage area 4 is changed, the program code storage area 4 is erased by the erase signal in the same manner as described above, and the changed data is written in the RAM 8. Next, the program of the bootstrap storage area 6 is executed to read the contents of the RAM 8 and write it in the program code storage area 4.

Embodiment 2. In the first embodiment described above, the transfer of data from the outside to the bootstrap storage area is
RAM externally attached to the one-chip microcomputer 7.
Although the case where the data is transferred via 8 is shown, it is also possible to transfer the data by using the serial communication function built in the one-chip microcomputer 7.

That is, the program of the bootstrap storage area 6 is prepared in advance for the system, and when the data is changed, the data to be changed is delivered to the bootstrap storage area 6 from the outside, and the bootstrap storage area is stored. The program in the area 6 rewrites the data in the area to be changed. As a result, even if the data is changed, the one-chip microcomputer 7 can change the program code and the data code while being mounted on the board.

[0015]

As described above, according to the present invention, the flash EEPROM having the program code storage area, the data code storage area, and the bootstrap storage area for writing the external data into the above areas is built in. Therefore, even if the program code and data code are changed frequently, it is not necessary to use a socket when mounting this one-chip microcomputer on the board, and it is also possible to change the data. There is no need to provide a ROM outside the computer, and the one-chip microcomputer is removed from the board independently of the program code or data code without any restrictions on the space on the board or the durability problem of sockets. Without any problem It is possible to change when needed to. Further, even when developing a one-chip microcomputer having a ROM for storing the program code and the data code, it is not necessary to develop a package having a glass window for erasing data by ultraviolet rays. ..

[Brief description of drawings]

FIG. 1 is a block diagram of a one-chip microcomputer showing a first embodiment of the present invention.

FIG. 2 is a block diagram of a conventional one-chip microcomputer.

[Explanation of symbols]

 1 CPU 2 Flash EEPROM 3 RAM 4 Program code storage area 5 Data code storage area 6 Bootstrap storage area 7 One-chip microcomputer

Claims (1)

[Claims] 1. In a one-chip microcomputer including a CPU, a RAM, a ROM, etc., a flash EEPROM used as the ROM, a program code storage area provided in the flash EEPROM, and a data code storage provided in the flash EEPROM. And a region provided in the flash EEPROM,
A one-chip microcomputer provided with a bootstrap storage area for storing a program for reading data supplied from the outside and writing the data in the program code storage area and the data code storage area.